This invention relates to a new and improved method for the production of inorganic fibrous dispersions and formation of continuous strands therefrom. More particularly, this invention relates to a novel method for the production of continuous strands, having improved characteristics, from relatively short inorganic fibers, particularly asbestos fibers.
The processes for forming filamentary or strand material may be broadly classified as (1) dry, (2) wet, and (3) melt spinning.
Dry processes for forming continuous filaments or strands from discrete fibers involve the use of relatively expensive equipment such as cards, spinning frames and other complex machinery and also create the usual dust problems attendant with the handling of dry discrete particles.
Conventional wet processes for forming inorganic fibrous strands usually involve the making of a water-laid paper which is slit and twisted. The known wet processes for directly extruding a continuous strand from inorganic fibers involve a chemical or thermal reaction of a colloidal fibrous dispersion whereby the dispersion medium is converted into a binding agent for the fibers or else a portion of the colloidal dispersion of fibers is converted into a binding agent.
The resultant products have a cementitious, twisted paper appearance, are relatively stiff and are deficient in the elongation requisite for high speed weaving and braiding operations. Furthermore, the production of strands from colloidal dispersions of asbestos fibers requires the use of a relatively large quantity of surface-active agents to sufficiently deflocculate or open asbestos fiber bundles to form the gelatinous colloidal dispersion. The preparation of the colloidal dispersions also results in such a drastic reduction of fiber length that a binder must be relied upon to define and maintain the integrity of strands formed therefrom.
The production of strand material by melt spinning is usually conducted by melting materials, such as synthetics (nylon and the like), glass, and others to form a solution which is extruded to form a continuous filament strand. In contrast, this invention is concerned with the production of a continuous strand from discontinuous relatively short fibers.